The present invention relates to an air pressure operated lubricating gun or apparatus for pumping lubricant out of a container such as a barrel or a drum holding the lubricant. A pneumatically driven barrel pump is the most important tool for manually performing a lubricating job. Such a pump makes it possible to withdraw the lubricant directly from its original container while simultaneously transporting the lubricant at low pressure for a volume conveyance as well as at high pressure for the lubrication proper.
The invention relates to an air pressure operated lubricating pump in which the air pressure motor drives the high pressure pump by means of an intermediate rod. The motor is automatically switched over when it reaches its end position. The high pressure pump conveys the lubricant, especially lubrication grease, directly from the containers into the lubricating conduit.
It is known in connection with such lubricating pumps to locate the control means for the air motor above, next to, or below the drive piston within special structural components such as a housing for these control means. The switch-over is preferably caused by means of a pull rod arranged inside the piston rod of the air motor and effective when the air motor piston reaches its end positions.
The high pressure pump may be arranged in the pipe which is immersed into the lubricant. The lubricant is conveyed through hollow spaces in the immersion pipe to a discharge port above the immersion pipe whereby the hollow spaces are arranged concentrically relative to the conveying piston. Conventionally, the immersion pipe comprises several structural components which are secured to one another by screwed connections in a high pressure sealed manner. The junctions, which cannot be avoided between two adjacent immersion pipe components, hinder the sliding of the follow-up piston on the outside of the immersion pipe which guides the follow-up piston. Thus, it is known to enclose the immersion pipe with a protective pipe which covers the junctions between adjacent immersion pipe components.
Due to the high construction costs of prior art air pressure operated lubricating pumps, they may be used economically only for a relatively small number of lubricating jobs.